The present invention relates to a process of precisely adjusting the lost travel of at least one piston in a master cylinder of a pressure fluid-operated brake system for automative vehicles. The master cylinder is the cylinder which is actuated by pedal force or an auxiliary force such as compressed air, a vacuum, or hydraulic pressure. The entire braking operation is initiated and controlled through the master cylinder wherein during application of the brake pedal, the master cylinder piston forces the brake fluid contained in the brake system into the disc brake and the wire cylinder.
Details of operation and design of master cylinders have been described in the "Brake Handbook", 9th edition, published by Bartsch-Verlag, Ottobrunn near Munich, pp. 34 to 73, and particularly pp. 34 to 37 and 52 to 55 thereof.
In order to vent the brake system and to establish a pressure balance between the brake system and the equilibrium reservoir at temperture fluctuations to be established, the cylindrical chamber of the master cylinder is in communication through an equilibrium port with the reservoir. Hence, a pressure build-up in the brake system can take place only if the latter closes the equilibrium port during actuation of the brake piston and, during its continued movement, compresses the remaining fluid within the cylindrical chamber. Consequently, a pedal movement of a predetermined length is required before a brake pressure can develop in the brake system. The distance covered by the piston from its initial position to the point at which it completely seals the equilibrium port during its continued movement, thereby to build up a pressure in the cylindrical chamber, is referred to as lost travel.
Master cylinders in brake systems are composed of a variety of individual components which are all manufactured with required tolerances. As the components frequently are disposed geometrically in series arrangement, the required tolerances sum up such that the total resulting lost travels can assume substantial values. Moreover, the lost travel in each master cylinder can assume a different value so that each brake responds to a different path of actuation.